Two trials were designed to study the relationships of
dietary fiber (ADF) and protein level and source to fecal
consistency in lactating cattle. In Experiment 1, 30 cows
(12 multiparous, 18 primiparous) were randomly assigned to
one of six total mixed diet treatments through four 21 d
periods. For Experiment 2, six primiparous cows were used
in two 6 x 6 Latin squares to evaluate water consumption,
apparent digestibilities of DM, AOF, NOF, and starch, and to
quantitate whole corn kernel passage. Total mixed diets for
both trials were formulated to contain 17% (LF) or 25% AOF
(HF) with CP levels of: 15% (S15) and 22% (S22) with soybean
meal (SBM) supplementation, or 22% (G22) with combination of
50% corn gluten meal (eGM) and 50% SBM. Two forage sources
were evaluated: corn silage (e) and alfalfa/corn silage (Ae)
(50:50 on OM basis). Fecal consistency was evaluated using
a 4 point scale (l-most fluid to 4-least fluid).

Dietary effects on fecal consistency were primarily due
to ADF level and type of protein supplement. Accurate
prediction of fecal consistency score from the dietary and
animal parameters identified was not possible. Further
study is suggested to evaluate different protein sources,
the contribution of water consumption, and to clarify
interactions of protein, forage source and fiber level in
relation to fecal consistency.